The present invention relates to a current sensor, and in particular to a current sensor comprising: a housing; a bus bar supported by the housing and connected to a battery post provided on a battery, the bus bar conducting a current; an annular shield plate arranged to surround the axis extending in the direction of flow of the current in the bus bar; and a magnetic-electric conversion element arranged on the housing for detecting the magnetic flux density of a magnetic field generated when a current has flowed in the bus bar to produce an electric signal.
FIG. 13 shows a related current sensor 1. The current sensor 1 includes a bus bar 3 as a conductor through which a current flows, a sensor housing 2 formed with the bus bar 3 inserted therein an annular core 4 as a shield plate arranged to surround the Y axis extending in the direction of current flow in the bus bar 3, a Hall IC 5 as a magnetic-electric conversion element for detecting the magnetic flux density of a magnetic field generated when a current has flowed in the bus bar to produce an electric signal, a circuit board 6 for mounting the Hall IC 5; an external output terminal (not shown), and a case 29. The Hall IC 5 is arranged in a space surrounded by the core 4.
On the current sensor 1 thus configured, a magnetic field is generated having a magnetic flux density corresponding to a current flowing in the bus bar 3. The Hall IC 5 converts the magnetic flux density of a magnetic field converged by the core 4 to an electric signal and outputs the electric signal as one corresponding to the current. The core 4 further has a feature to shield the influence of an external magnetic field.
The core 4 is provided so as to be divided into a first divided shield plate 4A and a second divided shield plate 4B. Each of the first divided shield plate 4A and the second divided shield plate 4B is arranged to be fixed to the outer side surface of the case 29. Just fixing the first divided shield plate 4A and the second divided shield plate 4B on the outer side surface of the case 29 allows the bus bar 3 to penetrate the core 4.
The current sensor 1 uses the first divided shield plate 4A and the second divided shield plate 4B as the core 4 and thus has problems of an increase in the number of parts and mounting man-hours.